Simian virus 40 small-t antigen binds two zinc ions.

Six cysteine residues of the simian virus 40 small-t antigen (small-t) are important for stability of the protein. Stability has been shown to be related to the ability of small-t to bind zinc ions in vitro. Purified small-t expressed either in bacteria or from baculovirus vectors binds two molecules of zinc per molecule of protein. Thus, small-t may resemble GAL4, which contains a Zn(II)2Cys6 binuclear cluster.